Telomerase, a ribo-nucleoprotein that counteracts telomere shortening, has recently been suggested as having a telomere independent survival function. A protective effect of telomerase on mitochondrial function under conditions of oxidative stress has been described, yet the exact mechanism and phenotype linked to mitochondrial or nuclear TERT (catalytic subunit of telomerase) is not clearly identified. We have shown that in the presence of coronary artery disease or acute vascular stressors, there is a shift in the mechanism of flow mediated dilation (FMD) from NO to H2O2. The current study aims to differentiate the role of nuclear TERT vs. mitochondrial TERT in the development of cardiovascular (CV) disease. In our central hypothesis, mitochondrial TERT plays a critical and previously undiscovered role in reducing mitochondrial reactive oxygen species (ROS) thus protecting against CV disease and other ROS associated disorders. This study will focus on CV health and use FMD and its mechanism and redox environment as physiological markers. The conceptual paradigm shift tested is that mitochondrial TERT decreases mitochondrial ROS production by improving mitochondrial respiratory chain activity. This contributes to maintaining normal NO levels, thereby preserving physiological regulation of FMD in the microvasculature. Conversely, we postulate that reduced mitochondrial TERT results in increased mitochondrial ROS, driving microvascular dysfunction by changing the mediator of FMD from NO to H2O2 thereby creating a pro-inflammatory milieu. We will be using state of the art methods to evaluate vascular reactivity alongside molecular evaluation of the redox environment to characterize the role of telomerase in regulating cellular and mitochondrial ROS levels. This novel hypothesis and the models generated have important translational potential and will be extremely useful for investigators studying varying diseases and in multiple fields.